Here is the fillet guy again.
See image. Is it possible to fillet those selected edges? I've tried all sorts of options but non works.
This is just a test/play around and I stumbled up on this problem.

I can't do it either in MoI - It's doable in Rhino so i can't figure why not in MoI. However, when trying to do a fillet in MoI you can see a hidden pair of lines appear so was your original model a cube by any chance, even ShrinkTrimmedSrf won't help either - Good puzzle!!

Hi Rich_Art - it's possible that the filleter doesn't know how to handle the patch area at the very top, but you've also got a different problem there in that you've previously filleted other edges that are running into the same area that you want to do now:

So because of that you've got a situation like this where you're only trying to fillet just this edge on the box example here:

That will confuse the filleter because by selecting only that edge and not the one above it you're telling it to try and open up a hole in the model something like this:

So when you've got something like that you need to select a longer range of edges including the one made from the previous sharp-cornered fillet like this:

Then the filleter will be able to try to put in a fillet like so:

So in order for the filleter to have a chance with your shape there, you will need to select those little tiny edges on the bottom areas where you've had that previous sharp-cornered fillets go.

But having stuff like some partial fillets placed with sharp meeting junctures in areas that collide with more edges that you want to fillet is not so good - it's better to do the filleting of such thing all in one go when the edges are interacting with one another like this - doing it all in one go allows the filleter to classify the places where things collide together as needing corner patches in it - by doing a sort of partial fillet before hand like you've done here the filleter now needs to actually consider the previous little fillets on the bottom and process them as things to construct new fillets between so it makes things more complex for the filleting if you do connected edges in separate batches like this.

Hi Rich_Art - did you previously try to do the fillet all at edges at once but had a problem with that?

Normally doing it all edges at once would have been better, except this particular kind of case with the multiple "disappearing" fillets (where the fillets pinch down to nothing at the end) has some problems in it.

So I guess that's probably why you ended up with the sort of partially done fillet in this case?

Also here's a different version of your model with the arches of slightly different height which avoids having that kind of "crown point" juncture - this version will fillet more easily doing stuff all at once since it avoids the "disappearing fillet" type situation.

>>Hi Rich_Art - did you previously try to do the fillet all at edges at once but had a problem with that?<<

Yeah I guess. Perhaps it is best to remake the whole object and try again to fillet it.

>>Also here's a different version of your model with the arches of slightly different height which avoids having that kind of "crown point" juncture - this version will fillet more easily doing stuff all at once since it avoids the "disappearing fillet" type situation.<<

Thanks but that is not wanted. :-)

There is a new tutorial on a C4D forum which shows how to make this. I thought, hey Moi can do this in 2 seconds. I was wrong lol.

Hi Rich_Art, yeah unfortunately that's a particular type of topology and shaping that the filleter has some trouble with.

Another technique that can sometimes help to make things easier on fillets in areas where it has trouble is to put a sort of "hub" where pieces are coming together, see the attached example, that one will fillet up to a radius of 0.2 when it seems to run into some trouble again.

A little tut that i made ;) (in French sorry )
Just 4 curves on 2 cube's faces are sufficient for make a complete boolean intersection
Select all / Construct / Boolean Merge
Just kill (or keep and move) the internal volumes!